Troubleshooting / FAQs
8.5 Step 4: Improving the application
SITRANS F C MC2
Operating Instructions, 10/2009, A5E02154544-02
35
If the sensor is disturbed by vibration from the pump, the installation should be improved
or the pump should be exchanged, e.g. to another type.
2.
Check for cross talk.
Turn off the power to the other flow meter(s) and wait approximately 2 minutes, so the
vibrating tubes in the sensor have stopped vibrating. Then check if the zero point stability
has improved, i.e. that the fluctuation in kg/h has been reduced. If this is the case, the
sensors disturb one another and the installation should be improved.
Air in the liquid
When air is present in the liquid, the zero point becomes unstable, which leads to a poorer
measurement accuracy.
Checking for air:
● Check the Driver Current
MASS 6000
SIFLOW FC070
Menu entry
Service mode ->
Special information
Online menu:
View ->
Device status
● Check if the "Driver current" varies more than ± 1 mA. If this is the case, it is usually due
to the presence of air or gas bubbles in the liquid.
● Increase the pressure in the sensor, creating a larger back pressure upon the sensor by
reducing the opening of the outlet valve or by increasing the pump pressure. Thereby the
size of air bubbles inside the sensor will be minimized. If the value or stability of "Driver
current" falls, it is proof that the liquid contains air or gas bubbles.
Typical causes of air in the liquid
● The entry pipe and sensor have not been properly filled with liquid. The pump cavitates,
the rotary speed of the pump is too high in relation to the supply of liquid to the pump.
● The flow rate in the pipe is too high, so components sitting in front of the flowmeter can
cause cavitation.
● If there is a filter installed before the flow meter, it may be close to blocking, which also
can cause cavitation.
Solid particles in the liquid
If the solid particles in a liquid have a density higher than that of the liquid, they can
precipitate inside the sensor and cause instability which leads to a measurement error.
If solid particles are present in the liquid, they must be homogeneously distributed and have
the same density as the liquid. Otherwise they can cause relatively large measurement
errors.
It is important that the sensor is installed such that solid particles can easily run out of the
sensor.